<template>
  <div id="container" v-show="show">
    <!-- <div class='pdf-page'> -->
      <canvas id="the-canvas"></canvas>
      <div class="foot" v-if='pdfDoc'>
        <button class='left' v-if="pageNum>1" @click="onPrevPage">上一页</button>
        <button class='right' v-if="pageNum<pdfDoc.numPages" @click="onNextPage">下一页</button>
        <button class='right' @click="close">关闭</button>
      </div>
    <!-- </div> -->
  </div>
</template>
<script>
import PDFJS from 'pdfjs-dist'
 
export default {
  data () {
    return {
      show:false,
      pdfDoc: null,
      pageNum: 1,
      pageRendering: false,
      pageNumPending: null,
      scale: 0.9
    }
  },
  methods: {
    showPDF (url) {
      let _this = this
      this.show = true
      PDFJS.getDocument(url).then(function (pdf) {
        _this.pdfDoc = pdf
        _this.renderPage(1)
      })
    },
    close(){
      this.show = false
    },
    renderPage (num) {
      this.pageRendering = true
      let _this = this
      this.pdfDoc.getPage(num).then(function (page) {
        var viewport = page.getViewport(_this.scale)
        let canvas = document.getElementById('the-canvas')
        canvas.height = viewport.height
        canvas.width = viewport.width
 
        // Render PDF page into canvas context
        var renderContext = {
          canvasContext: canvas.getContext('2d'),
          viewport: viewport
        }
        var renderTask = page.render(renderContext)
        canvas.style.width = '100%'
        // Wait for rendering to finish
        renderTask.promise.then(function () {
          _this.pageRendering = false
          if (_this.pageNumPending !== null) {
            // New page rendering is pending
            this.renderPage(_this.pageNumPending)
            _this.pageNumPending = null
          }
        })
      })
    },
    queueRenderPage (num) {
      if (this.pageRendering) {
        this.pageNumPending = num
      } else {
        this.renderPage(num)
      }
    },
    onPrevPage () {
      if (this.pageNum <= 1) {
        return
      }
      this.pageNum--
      this.queueRenderPage(this.pageNum)
    },
    onNextPage () {
      if (this.pageNum >= this.pdfDoc.numPages) {
        return
      }
      this.pageNum++
      this.queueRenderPage(this.pageNum)
    }
  }
}
</script>
 
<style scoped>
#container {
  background-color: rgba(0,0,0,0.75);
  position:fixed;
  width: 100%;
  height: 100%;
  top: 0;
  left: 0;
  text-align: center;
  padding: 5px;
  z-index: 2000;
  overflow: scroll
}
 
.foot {
  position: fixed;
  transform: translate(-50%,0);
  left: 50%;
  z-index: 3000;
  bottom: 10px;
 
  
}
.foot button{
 padding: 6px 20px;
}
</style>
